Propeller



H. FAEHRMANN.

I PRoPELLERv.' APPLICATION FILED 0CT.27, I9I5.

1,358,430. l Patented Nov. 9, 1920.

2 SHEETS-SHEET 1.

Y :d w 6,

/V VEN TUR /rJ/MJUL 15e/217mm H. FAEHRMANN.

PaoPELLER.

Y APPLICATION FILED OCT-27,1915. 1,358,430', Patented Nov. 9, 1920.

40 2 SHEETS-SHEET 2.

W/T/VESS:

aan STATES HERMANN FAEHRMANN, OF BROOKLYN, NEW YORK.

PROPELLER.

.i ,atenerse Specification of Letters Patent.

Patented Nov. 9, 1920.

Applicationled October 27, 1915. Seria] No. 58,094.

i! 'o uZZ rtf/lont 'it lmay concern.'

lie it known that l, HERMANN FAEHRMANN, a citizen of the United States,and resident of the borough of Brooklyn, county of Kings, city and Stateof New York, have invented certain new and useful Improvements inlhaipellers, of which the following is a. specification.

My invention relates to screw propellers .lor aerial or aquaticnavigation, and has for its object to provide an exceedingly efiicientpropeller of great simplicity of construc- 'tion and susceptible ofoperation at Very h igh speeds. Experiments which l have beencondactingl for years have confirmedthe corria'tness of my opinion thata high number of revolutions is conducive to an increased ellicienoy ofsuch propellers, and my present improvement is designed especially inview ol usingr a high rotary speed.

tiercral examples of .my invention will now be described in detail withreference to the accompanying drawings, and the novel features will thenbe pointed out in the apjicuded claims.

Figure. l is a side View of one form of my inijpiroved propeller, Fig. 2'is an end View Vthereof. Fior. 3 is a partial longitudinal section. onan enlarged scale, on line .33 of iiigr. f3. and Fig. l is a crosssection on line gimiol` Fin'. Si. the propeller blade being omitted;Vie'. 5 is a front View of a second forni oi' my invention. and Fig. (lis a section on line l--ft of Fig'. shown on an enlarged scale: tig'. Tis a longitudinal apj'n'oximately central scr-tion of a third form of myinvention. taken on line 'i1-7 of Fig'. 9. Fig". 8 is a kif'ertii-alsection on line tl-8 of Finn i, shown on an enlarg'eifl scale, Figi'. 9is a top View of this forni of my inrention, with part-s in section, andFig. l is a detail cross section au line -l0 of Fig'. i; Figi'. il. is across vsection similar to Fin'. S of still another forni Til.' myinvention. Fig. l?) is a section on the lino lil-42 .of Fig'. ll, andFig. 15:3 is a partial section. of the same character as Fig. L7. butshowing the form of my invention vllustratell by Figs. ll and l2.

The leadingr feature of my improved pro* .icllcr structure asrepresented in the drawuns is the provision of a single propeller Blade.and proper means for coilnterbalancne' it. ln the particular embodimentof my in'cnl'ioii shown in Figs. l to -l. the blade it great thinness,extends farthest out at one side, and is comparatively narrow, measuredcircumferentially, at said side, while the other portions of the bladeproject less and less from the center or axis, but increase in width,measured circnniferentially. That 1s, the outer edge of the blade formsa helical spiral which` gradually approaches the center as the bladegrows wider circumferentially. The pitch of the blade should be smallfor the securing of the best results, and I have found it desirable touse a pitch angle not exceeding 150 at the outer edge of the tip (L ofthe blade. The pitch angle is defined as the angle which the helical orscrew-line of the propeller blade, at any point thereof, forms with aplane laid through said point j ierpendicnlar to the axis of rotation.As shown in Figs. l and 2, 'the length of the Iblade A, measured in adirection parallel to said axis, is approximately equal to the maximumdistance to which the blade projects radially from the carrier or hub B(at the tip a). Preferably the pitch angle increases gradually from saidtip a to the other end of the blade that is to say, the pitch issmallest at that end of the blade which projects farthest from the axis,and greatestat the opposite end of the blade (rightdiand end in Fig'. l)blade is connected rigidly with the hub B, as by casting it integralwith said hub. The latter is pointed at the free, end B', and is shownprovidedat its other end with a. shoulder B adjacent to a shoulder C onthe propeller shaft (l. The pointed end B of the hub is represented as aseparate piece, secured to the hub body B by screws D and nuts D', thelatter conntersunk in recesses and readily accessible from the outside.The outer end of the shaft C, which is screwthreaded, is containedwithin the end or cap l. and receives' a nut E serving to secure the hubon the shaft. and. as shown, the latter and the axial bore of the hubmay bc tapered so as to increase the holding action oi" the nut lil. Ufcourse, the hub may be secured to the shaft in any other approvedmanner. The hub is cored out, asindicated at lk. on the side on whichthe blade .l projects farthest out. so that the side ol' the hubopposite to said blade portion may be heavier and assist in balancing`the blade and hub structure. As shown. the blade extends entirelyVaround the hub. so that one portion of the blade is utilized as This apartial counterbalance for another blade portion; the maincounterbalancing effect, however, is obtained by coring out the hub atBf, the form of the cavity being shown in Figs. 3 and L1, that is tosay, the cavity is arched both lengthwise and transversely. The outersurface of the hub B, B is torpedoshaped, that is to say, of circularcross section at every point, and tapering toward both ends from thecentral or widest por tion at which the blade A is placed. The blade andhub are balanced in two senses: first, the weight is balanced, that isto say, if the shaft C is horizontal the blade and hub, if turned to anyparticular position and stopped, will have no tendency to shift fromsuch position; second, there is also balance of axial thrusts orpressures, that is to say, the sector containing the outer or tipportion of the blade exerts the same pressure on the air or water as thesector of equal angular extent diametrically opposite said tip portion;this latter result is due to the fact that the width of the blade, measured circumferentially, as well as the pitch angle of the bladeincreases from the `tip toward the other, inner end of the blade. Itwill be observed that at the end or tip where the blade projectsfarthest from the axis (left-hand end in Fig. 1), where the outerportions of the blade have the highest linear velocity, the pitch angleis smallest, and the width of the blade, measured circumferentially, isleast, both the pitch angle and the width of the blade, measuredcircumferentially, increasing toward the other` end of the blade, wherethe blade does not project so far from the axis (right-hand end inFig. 1) and where therefore the linear velocity is relatively low. 0fcourse, the linear speed is in direct ratio to the distance from theaxis, and on the other hand, other things being equal, the axial thrustor pressure increases with the pitch angle. periments have demonstratedthat with a high linear speed` the best results are obtained when thepitch angle is small, while with a low linear speed, the best resultsare obtained with a relatively greater pitch angle. The balancing of theaxial thrusts or pressures on different portions of the blade isobtained by a proper proportioning of the three factors, viz.:circumferential width of the blade, its radial. extent or projectlonfrom the axis, and the pitch angle. Thus, with my improved propeller,the radial length of the helical blade decreases from front to rear,while the pitch increases in the same direction.

The propeller shown in Figs. 5 and G differs from the one illustrated byFigs. 1 to i by the provision of ribs A directed toward the shaft C, onthe forward side of the blade A, that is the side toward which the boator airship is traveling. These ribs, which may be cast integral with theblade, stiften it considerably, and enable it to better resist theconsiderable strains due to centrifugal force when the blade is rotatedat a high speed. The effect of centrifugal force iU beneficial in mypropeller, inasmuch as it counteracts the tendency of the pressure tobend the blade lengthwise of the. shaft. Fig. 5 also shows that theblade, instead .of continuing through about 3G00, may be made to extendthrough a smaller angle, but its general shape, and the manner ofbalancing it, are the same .as described above.

According to the construction shown in Figs. 7 to 10, the 'hub body ismade of two spaced sections B and Bb, with rings or collars Bc,interposed between them. These rings have openings Bd which registerwith each other and also with cavities Be and Bf in the hub bodyportions Ba and Bb respectively, forming together a cavity similar inarrangement and purpose to the one shown at B* in the form of myinvention Erst described. The collars Bc engage the shaft C, and haverecesses lig at their inner portion to receive the feet A* of ribs Awhich are held individually within lrecesses B in the adjacent faces ofthe outer portions of the rings or collars B, the two end recessesextending into the end faces of the hub body portion. The blade Aa isshown of substantially the same form as in Fig. 5, but is a separatemember secured to the ribs A in any suitable manner, as by rivetsPreferably the width of the collars Bc increases from left to right. Lasshownin Figs. 7 and 9, so that the pitch angle will be increased fromthe tip of the blade to the other end. The inner ends of the ribs A, atthe feet LW, are perpendicular to the axis of the shaft, but the outerrib portions are twisted (Fig. 10) so as to bring them into an aliningposition substantially like the one shown in Fig. 6. The outer portionsof the ribs are half-round, the blade being applied against the fiatsurfaces. The cross sections in Fig. 9 show the ribs where they emergefrom the hub. lf desired, pins F may be provided to anchor the rings Bcto the lbody portions of the hub.

Figs. 11, 12 and 13 illustrate a construcl tion differing from the oneshown in Figs. '7 to 10, by the construction of the blade in sectionsinstead of one piece, and the con nection of these sections with eachother and with the ribs. and also by the manner of securing the ribs onthe shaft. Each of the blade sections Ab is made integral with one ofthe ribs AC, and the free edge of each blade section is suitably securedto the next following rib, as by rivets 7J. Figs. 11 and 13 also show adifferent construction of the inner portions of the ribs, which latterin these two views are shown as formed integral with rings d fittingaround the shaft C (shown square). In other respects, this constructionis substantially the same as in Ifig's. T to l0.

The torpedo shape of the hub also increases the cliciency of thepropeller, such shape preventing injurious whirling of the water or airthrough which the boat or airship (or aeroplane) is being` propelled.

The constructions illustrated by Figs. 5 to 13 may if desired be appliedto a blade of large circumferential extent (such as shownin Figs. l and2).

While I have described my improved structure as a. propeller for aerialor aquatic navigation, it will be obvious that it may be employed forother purposes, thus, when driven by connection With an engine, thestructure may also be used as a ventilator (fan) or pump, or, whenexposed to the action of a current of air, water, gas or steam, thedevice will be available for use in turbines, water-motors, anemometers,meters for water and gas, ete-For use in water, I prefer to employ acomparatively long blade (as in Figs. l to 4), while when the bladeworks in air, I prefer a shorter blade (as in Figs. 5, 8 and 1l) Thebalancing of the rotary structure may also {be-.obtained by making theportion of the blade on the lower side of the shaft (Fig. 2) heavierthan the portion on the opposite side of the shaft, which result can beobtained by varying the thickness of the blade (or of the ribs, whenthey are employed). Furthermore, by making the shaft very heavy, I maysecure a practically suliicient approximation to a perfect balance, theshaft being then able to bear all the strains even though the bladeitself is not fully balanced.

Various modifications may be made without departing from the nature ofmy inventon as set forth in the appended claims.

I claim as my invention:

l. A structure adapted for use as a propeller or for other purposes,provided with a helical blade whose radial length is greatest at one endof the helix and decreases toward the other end of the helix, while thewidth of the blade, measured circumferentially, and its pitch angle bothincrease gradually from the portion of greatest radial length to theopposite end of the helix, said radial length, circumferential Width,and pitch angle being proportioned to balance the pressures on differentportions of the blade in the direction of axial thrust.

2. A structure adapted for use as a propeller' or for other purposes,provided With a helical blade whose radial length decreases from one endof the helix to the other while its pitch angle increases in the samedirection, the parts of the blade being proportioned to balance thepressures exerted in the direction of axial thrust, on diametricallyopposite blade sectorsof like angular extent.

3. A structure adapted for use as a propeller or for other purposes,provided with a helical blade whose radial length decreases from frontto rear, while the pitch angle i11- creases in the same direction, theparts of the blade bein,fr proportioned to balance the pressures exertedin the direction of axial thrust, on diametrically opposite bladesectors of like angular extent.

4. A structure `adapted for use as a propeller or for other purposes,provided with a hub which is'heavier on one. side than'on the other, anda blade different portions of which project to different distances fromthe hub, the portion of the blade which projects farthest out,l beinglocated on the lighter side of the hub.

A. structure adapted for use as a propeller or for other purposes,provided with a hub having an interior cavity whereby the hub is madeheavier on one side than on the other, and a blade different portions ofwhich project to different distances from the hub, the portion of theblade which projects farthest out, being located on the lighter side ofthe hub.

In testimony whereof I have signed this specification.

HERMANN FAEHRMANN.

